I'm in the middle of designing a desk that will have to support several hundred lbs., but I'm unsure of what would be the simplest method of bracing to carry a significant amount of weight. All my research has dug up are fancy desks that promote form over function, and tend to be on the small side, like a writing desk. What I'm envisioning is a strong worktable-type unit that is low enough to sit at, about 8-10 feet long with no drawers or shelves. While I'm confident in my plans, what worries me is that I'll design it to be too weak. What is a simple, cost-effective way to design such a brace?
I think this is what you described.
Not to get really in depth because your tastes are your tastes but if you are looking for a lot of weight and performance I would make the legs out of 4x4s and the top/bottom trim out of 2x6's, attaching the 4x4s to the 2x6s with 2 lag bolts in each post - corners would have 4 bolts - 2 on each side.
Edit: There should be the sets of lag bolts (so 4 for corners) on both the top and bottom of the leg. If we look at the picture in the other answer they have 6 legs - 4 are corners. There would be a total of 40 lag bolts in that. I have built tables like this when I need them to be free standing. Nice thing about this too is that you can take it apart and move it if needed. Think IKEA but sturdier materials.